Solid tumors comprise the majority of human cancers. These constitute the major challenges in our national efforts to improve the diagnosis and treatment of cancer. One of the primary objectives of this Division has been the establishment of a solid tumor model which could serve both as a system for devising improved therapeutic scheduling and for a better understanding of neoplasms in general. Studies of the growth and cell proliferation kinetics have been completed on 9 different experimental tumors. Studies in vivo on the effects of 5-fluorouracil have been extended to both the very rapidly growing hepatoma 3924A and the very slowly growing hepatoma 16. Studies have been completed on the cell cycle times, potential and actual volume doubling times, cell loss factors and growth fractions. These studies on two markedly different tumors should permit a greater generalization about results from the effects of therapy. The collaborative studies to ascertain the correlation between the growth rate and cell kinetic characteristics of hepatomas 3924A and 16 and different blood, urine, tumor, and liver constituents have also been extended. Collaborative in vivo and in vitro studies are now being carried out by high speed flow microfluorometry on single cells to evaluate changes following therapy. Collaborative studies are being initiated to evaluate changes in different tumor cell populations after therapy by scanning microphotometry and automatic computer analysis. Two hepatoma cell lines have been established from the 9 hepatoma lines originally studied. These two in vivo - in vitro tumor systems for solid tumor models should permit a more precise and more quantitative evaluation of the effects of radiotherapy, chemotherapy, immunotherapy and surgery. Therefore, the objective of the work proposed in this supplemental grant is to more fully develop these in vitro systems to complement the in vivo studies now in progress.